Phosphorescence In Eu2 Research Articles

Long-persistent phosphorescence in Eu2+-doped calcium borate chloride for optical data storage

Yellow-emitting optical data storage phenomena were observed in a series of Ca2BO3Cl: Eu2+, Ln3+ (Ln = La, Ce, Pr, Sm, Gd, Tb, Ho, Tm, Yb, Lu) long-persistent phosphors. Eu2+ in Ca2BO3Cl could emit yellow light located at 580 nm ascribed to the 5d-4f transitions when optical data was being read out. As co-activators, Ln3+ had various effects in causing afterglow and changing trap concentration. Optical data storage phenomena occurred for each combination of Eu2+ and Ln3+ in calcium borate chloride host. Thereinto, prepared Ca2BO3Cl: Eu2+, Ce3+ phosphor presented a decent afterglow and optical storage property. Its afterglow decay time was more than 1 h at room temperature and had a bright yellow optical signal at 473 K Ca2BO3Cl: Eu2+, Ho3+ showed an optimum optical storage property, which remained bright yellow light even after 7 days of data storage. This outstanding optical data storage performance was mainly derived from Ho3+ increased the trap concentration of oxygen vacancies. The crystal structure, excitation and emission spectra, afterglow decay curves and thermoluminescence curves were measured and analyzed in all Eu2+ and Ln3+ doped Ca2BO3Cl samples. A simple optical data storage method was set up and effective optical signals were observed. Based on these results, detailed optical data storage processes and possible mechanism were studied and discussed.

Temperature dependence of persistent phosphorescence in Eu2+-doped Ba3SiO5

Temperature dependence of decay curves of persistent phosphorescence in Eu2+-doped Ba3SiO5 crystals indicates that there are, at least, three electron–hole recombination centers. The decay curve from the dominant center is represented by I(t)=(A/t)(exp(−t/τ1)−exp(−t/τ0)) or I(t)=A/tn (n>1) below or above 360K, respectively. The integrated intensities of the decay curves decrease drastically in increasing temperature above 360K. As such temperature behavior is very similar to that of the intrinsic Eu2+ luminescence with short decay times of less than 2.7μs in Ba3SiO5, the deexcitation occurs through thermally multi-phonon assisted nonradiative relaxation to the ground state of Eu2+ in Ba3SiO5.

Effects of distorted lattice and nonequal-valvence substitution on the long lasting phosphorescence of Eu2+ and Gd3+ doped RMg2(PO4)2 (R=Sr,Ba) phosphors

The afterglow of Eu2+ activated SrMg2(PO4)2 can be greatly enhanced by the codoping of Gd3+, as well as an interesting phenomenon of the improvement of the efficiency of the excitation light. However, Eu2+ activated BaMg2(PO4)2 does not show the phosphorescence until the codoping of Gd3+. It is suggested that the codoping of Gd3+ improve the electron storage ability of material by acting as electron-trapping centers resulted from the nonequal-valence substitution of Gd3+ replacing Sr2+ and Ba3+. And the Gd3+-induced enhancement of the excitation efficiency of Eu and Gd codoped SrMg2(PO4)2 is due to the improvement of the energy transfer efficiency caused by the distortion of lattice of Gd3+ located at the sites of Sr2+.

Greenish-yellow Light-emitting, Long-lasting Phosphorescence in Eu2+-doped CaO–CaBr2–SiO2 Phosphor System

Abstract Novel greenish-yellow light long-lasting afterglow material, Eu2+-doped CaO–CaBr2–SiO2 phosphor system, is prepared by the conventional high-temperature solid-state method. Photoluminescence (PL) spectrum reveals that it exhibits a strong blue emission band centered at 469 nm with some asymmetry on the long wavelength side, while this phosphor emits greenish-yellow light and shows strong long-lasting phosphorescence after it is excited with 365-nm UV light. The phosphorescence lasts for more than 1 h in the light perception of the dark-adapted human eye (0.32 mcd/m2). The possible phosphorescence mechanism is also investigated.

Relaxation of ultraviolet-radiation-induced structure and long-lasting phosphorescence in Eu2+-doped strontium aluminosilicate glasses

We report on the relaxation of ultraviolet-radiation-induced structure and long-lasting phosphorescence in Eu2+-doped glass samples with compositions of xAl2O3 · 40SrO · (60 − x)SiO2· 0.05Eu2O2 · 0.05Dy2O3 (x = 0, 10, 30) (mol%). After irradiation by an ultraviolet lamp (λmax = 254nm) with a power density of 5 mW/cm2 for 30 min, a visible light (peaking at 510 nm) could be seen with the unaided eye in the dark even 24 h after the removal of the activating light. Thermostimulated luminescence glow curves, x-ray absorption, and electron-spin-resonance spectra were measured. We suggest that the long-lasting phosphorescence in the Eu2+-doped glass samples resulted from the recombination of electrons and holes at shallow traps in the glass matrix that can be thermally released at room temperature, and energy transfer between the recombination centers and Eu2+ ions.